The present invention relates to generally an improvement of choppers or vibrators and more particularly a chopper wherein when an output voltage is low, a maximum allowable output current may be increased by the transformer action and a pulsation factor may be considerably decreased as compared with prior art choppers.
In FIGS. 1 and 2 there are shown two examples of the prior art choppers. Reference numeral 1 denotes a DC power supply; 2, a switch; 3, a load; 4, a circulation diode and 5, a smoothing reactor. As is well known in the art, the switch 2 is alternately opened and closed by various methods and a maximum current flowing through the load is restricted by a maximum allowable output current of the switch 2 independently of an output voltage. Therefore when the load 3 is a DC drive motor of a rolling stock or the like, a greater current is required when accelerated; that is, at a low voltage as compared when driven at high speeds; that is, at high voltages. In order to provide a maximum current at acceleration, a current capacity of switching elements must be increased.